Sydney Roosters head coach Trent Robinson has branded the behaviour of Mitchell Pearce "unacceptable" after standing him down from all training commitments pending an investigation into a lewd act caught on video.

"For us, it is between us and the NRL to resolve. We will let you know when that time comes," he said.

"The behaviour was unacceptable. We understand that. We can't accept that and we won't."

The Daily Telegraph reports that Pearce could be stripped of the club's captaincy and fined up to $50,000, and is likely to be banned from travelling to the UK for next month's World Club Challenge.

In the video obtained by A Current Affair, a clearly inebriated Pearce is seen making advances towards a fellow partygoer and being reprimanded for urinating on himself and a couch at a home in Sydney late on Australia Day.

After being rejected by the woman, he can be seen turning his attentions to a Maltese terrier and simulating a lewd act on the dog as its owner tries to snatch it away.

A Roosters official told the Telegraph that Pearce, 26, would undergo counselling and have a permanent alcohol ban enforced.